Tantalizing tortoises and the Darwin-Galápagos legend.

Abstract

During his historic Galápagos visit in 1835, Darwin spent nine days making scientific observations and collecting specimens on Santiago (James Island). In the course of this visit, Darwin ascended twice to the Santiago highlands. There, near springs located close to the island's summit, he conducted his most detailed observations of Galápagos tortoises. The precise location of these springs, which has not previously been established, is here identified using Darwin's own writings, satellite maps, and GPS technology. Photographic evidence from excursions to the areas where Darwin climbed, including repeat photography over a period of four decades, offers striking evidence of the deleterious impact of feral mammals introduced after Darwin's visit. Exploring the impact that Darwin's Santiago visit had on his thinking--especially focusing on his activities in the highlands--raises intriguing questions about the depth of his understanding of the evolutionary evidence he encountered while in the Galápagos. These questions and related insights provide further evidence concerning the timing of Darwin's conversion to the theory of evolution, which, despite recent claims to the contrary, occurred only after his return to England.

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Tantalizing Tortoises and the Darwin-Gala ´ pagos Legend
FRANK J. SULLOWAY
Institute of Personality and Social Research
University of California
4125 Tolman Hall
Berkeley, CA 94720
USA
E-mail: sulloway@berkeley.edu
Abstract. During his historic Gala ´ pagos visit in 1835, Darwin spent nine days making
scientific observations and collecting specimens on Santiago (James Island). In the
course of this visit, Darwin ascended twice to the Santiago highlands. There, near
springs located close to the island’s summit, he conducted his most detailed observations
of Gala ´ pagos tortoises. The precise location of these springs, which has not previously
been established, is here identified using Darwin’s own writings, satellite maps, and GPS
technology. Photographic evidence from excursions to the areas where Darwin climbed,
including repeat photography over a period of four decades, offers striking evidence of
the deleterious impact of feral mammals introduced after Darwin’s visit. Exploring the
impact that Darwin’s Santiago visit had on his thinking – especially focusing on his
activities in the highlands – raises intriguing questions about the depth of his
understanding of the evolutionary evidence he encountered while in the Gala ´ pagos.
These questions and related insights provide further evidence concerning the timing of
Darwin’s conversion to the theory of evolution, which, despite recent claims to the
contrary, occurred only after his return to England.
Keywords: Charles Darwin, Gala ´ pagos Islands, Gala ´ pagos tortoise (Geochelone nigra),
introduced species, ecological disturbance, field work, Darwin’s conversion to
evolution, Darwin legend
Introduction
Of the various locations that Charles Darwin visited during his five-week
exploration of the Gala ´ pagos Islands in September and October 1835,
almost all have previously been identified (Estes et al., 2000; Sulloway,
1982b, 1984, 2002, 2005). The principal exception is the location of the
‘‘springs’’DarwinvisitedinthehighlandsofSantiago(JamesIsland),where
heandfourotherBeaglecrewmemberscampedforninedays(8–17October
1835).Itwas at these highlandsprings thatDarwin made hismost detailed
Journal of the History of Biology (2009) 42:3–31
DOI 10.1007/s10739-008-9173-9
? Springer 2009

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andmemorableobservationsaboutGala ´ pagostortoises–thoselumbering
and docile giants that helped him to revolutionize the history of science.
Whathappened,andperhapsmoretothepointwhatdidnothappenduring
Darwin’s visit to these remote highland springs, turns out to be critical to
understandingtheoriginsandtimingofhisfirststepstowardtheDarwinian
revolution. A notable omission by Darwin during his visit to the Santiago
highlands – namely, his failure to collect an adult tortoise for taxonomic
analysis – was to haunt him for nearly a decade owing to its critical
importance to his theorizing about speciation. Santiago was the last of the
four islands Darwin visited in the Gala ´ pagos, and a reconstruction of his
activities during his nine-day exploration of this island helps to establish
the mindset with which he reacted to ‘‘that great fact–that mystery of
mysteries–the first appearanceofnewbeings on this earth’’(1845, p.378).
The sites that Darwin visited near the highland springs are also note-
worthy for another reason. These localities have been subjected to dra-
matic ecological changes that have occurred since his visit, owing to
depredation by introduced feral mammals. Such ecological transforma-
tions, which Darwin anticipated after witnessing some of the deleterious
effects of early Gala ´ pagos settlers, exemplify the vulnerability of island
ecosystems. In the Origin of Species Darwin (1859) later discussed the
fragilityofislandecosystemsaspartofhiscritiqueofthetheoryofDesign.
On8October1835DarwinandhisfellowBeaglecrewmemberslanded
atBuccaneerCoveonthenorthwesternsideofSantiago,wheretheymade
camp.TheretheyencounteredapartyofSpanish-speakingcolonistsfrom
the newly founded Ecuadorian settlement on Floreana (also known as
CharlesIsland).SenttoSantiagobythecolony’svice-governor,thesemen
were busy fishing and hunting tortoises, and preserving their catch with
salt obtained from a crater lake at James Bay, 8 kilometers to the south.
During their stay at Buccaneer Cove, Darwin and his four Beagle com-
patriotsemployedseveralofthese‘‘Spaniards’’(asDarwincalledthem)to
bringthemfreshwaterfromaseepatCerroCowan,a284-meter-hightuff
cone that forms the southwestern side of Buccaneer Cove (Figure 1).
Much of Darwin’s geological research on Santiago was devoted to
understanding the origins of these sandstone-like tuff cones, which he
identifiedas‘‘themoststrikingfeatureofthisArchipelago’’(1844,p.112).
Darwin was the first geologist to realize that such cones are formed by
submarine mixtures of rising magma and seawater, which create aerial
explosions that fall back to earth as muddy rain (Darwin, 1844, p. 99;
McBirney and Williams, 1969, p. 3; Simkin, 1984, p. 72). As Darwin also
noted, the submarine origin of tuff cones explains why these structures –
unlike lava craters – are always found near the coast. Traveling by whale
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boatinthecompanyofthevisitingFloreanasettlers,Darwininvestigated
another prominent tuff cone on Santiago – the crater at James Bay from
which the Spaniards were extracting salt (Figure 2).
Darwin’s Route to the Santiago Highlands
Based on information contained in Darwin’s (1835a, p. 723) unpub-
lished ‘‘Geological Diary,’’ we know that he proceeded toward the
island summit on ‘‘a SE line’’ from his campsite at Buccaneer Cove. He
made this trek to the highlands with one of the Spaniards, who served as
his guide, and he was also likely accompanied by his servant and
collecting assistant, Syms Covington.
Darwin’s route to the highlands first took him to a height of ‘‘per-
haps 2,000 ft’’ (610 meters). ‘‘Our walk,’’ he (1988, p. 361) commented
in his personal journal, ‘‘was a long one,’’ and he estimated the distance
he had traveled from the coast to be about 6 miles (9.7 kilometers). At
this highland location Darwin (1988, p. 361) encountered two more
Spaniards who had erected ‘‘a couple of hovels’’ to protect themselves
Figure 1. The view toward Cerro Cowan, a prominent tuff cone on the southwestern
side of Buccaneer Cove. An endemic lava lizard (Microlophus albemarlensis) basks in
the sun to the right. Darwin and his party landed on the beach below. Their campsite
was located about 70 meters to the left of where this photograph was taken. (Unless
otherwise indicated, all photographs are by the author.)
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from the elements. These two men were busy hunting tortoises for the
meat, which they were salting, drying, and sending back to the settlement
on Floreana, 130 kilometers to the south, where tortoises were nearly
extinct. The hovels at which Darwin stayed no longer exist today. In
1906 Rollo Beck, a collector for the California Academy of Sciences
Expedition, observed remains of the Spaniards’ camp, which was still
littered with the bones of butchered tortoises (Pritchard, 1996, p. 67).
The camp was probably located a little beyond the present NationalPark
exclosure in this area (at S00? 11.300¢, W90? 47.798¢, measured from the
southeastern corner, where the elevation is 556 meters or 1,824 feet).1
Figure 2. An extensive lava field at James Bay on Santiago, which Darwin visited on
11 October 1835. In the foreground is a lava cactus (Brachycereus nesioticus), one of
the first colonists of such barren lava flows. Accompanied by a party of settlers,
Darwin investigated the tuff crater at the upper left, descending to the salina inside.
To reach this crater, Darwin and his companions walked across the lower portion of
this lava flow from their landing site, which was likely on a small beach to the
crater’s right. Visible in the far distance are three of the six volcanoes of Isabela
(Albemarle), an island on which Darwin landed briefly before arriving at Santiago.
1All GPS measurements are based on the World Geodetic System datum of 1984
(WGS-84), which is the only world referencing system available today (and the default
datum in most commercial GPS units, as well as the datum used by Google Earth).
These measurements have a horizontal accuracy of approximately ±10 meters. Mea-
surements of altitude were determined with a barometric altimeter, calibrated at sea
level, and have a similar accuracy.
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Darwin first ascended to the area of the hovels on 9 October,
returning to Buccaneer Cove the same day. He walked up to the hovels
again on 12 October, bringing with him a sleeping blanket so that he
could stay the night and collect extensively in this fertile region (Darwin,
1988, p. 361). While visiting at this highland camp, Darwin dined
exclusively on tortoise meat, remarking in this connection: ‘‘The
breastplate roasted (as the Gauchos do carne con cuero), with the flesh
attached to it, is very good; and the young tortoises make excellent
soup; but otherwise the meat to my taste is very indifferent’’ (1839,
p. 459). On 13 October, after the better part of two days spent collecting
in this region, Darwin returned again to Buccaneer Cove.
Sometime during Darwin’s stay at the hovels he climbed ‘‘an addi-
tional 1,000 ft’’ (305 meters), passing what he described as ‘‘a very per-
fect Crater,’’ which he estimated to be about 8 miles from the coast
(1835a, p. 723; 1988, p. 361). As Estes et al. (2000) have concluded, this
object of Darwin’s geological interests is almost certainly the distinctive
crater at Jaboncillos– an area named for the jaboncillo or soapberry trees
that used to grow there. This crater can be found just above where a
small National Park shelter collects water from fog and rain (at S00?
12.328¢, W90? 47.110¢, measured at the western base; elevation 819
meters or 2,687 feet). With its jagged features, Darwin’s perfect crater
can be seen from James Bay and Puerto Egas, localities regularly visited
by tour ships on the western side of Santiago, 9 kilometers away. Pro-
ceeding upward from this crater, Darwin would have reached the island’s
summit, about 90 meters higher up, by walking only 20 minutes more.
The Summit Pond
If Darwin did ascend to the summit of Santiago along the same
southeastern line he had previously been following, he would have
arrived at the top within 100 meters or so of a large and distinctive rock
nicknamed El Mun˜eco, owing to its striking resemblance to a puppet.
From this general vantage point Darwin would have found himself
looking down into a bowl-shaped area to the east, which is approxi-
mately 400 meters in diameter and is adorned by numerous large
boulders on its lower flanks. At the bowl’s center, occupying an area
about 25 meters across, water sometimes pools depending on the season
and the amount of recent precipitation. In addition, four small rivulets
run down into this pond from different sides of the bowl. The center of
this pond is located at S00? 12.700¢, W90? 46.908¢; elevation 887 meters
or 2,910 feet (Figure 3).
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One difficulty in determining exactly where Darwin went during this
excursion to the Santiago highlands is that his reports about the dis-
tances he traveled, and the corresponding elevations he attained, do not
coincide. Darwin’s estimates of the distances involved appear to be the
source of these discrepancies, as the amount of hiking required to attain
heights of 2,000 and 3,000 feet is only 2.7 and 4.2 miles, rather than the
6 and 8 miles that Darwin himself reported. Because much of the terrain
over this route is characterized by thick vegetation and difficult footing,
it is likely that Darwin overestimated the distance he walked given the
time it took him to reach Jaboncillos (3–4 hours, or longer if he stopped
to collect specimens). In addition, Darwin’s (1835a, p. 769) estimate of
the highest point on Santiago – which he placed at ‘‘about 3000 ft’’ – is
within 25 feet of the actual elevation (2,975 feet), reinforcing the con-
clusion that his reports about elevations are substantially more accurate
guides to his Santiago itinerary than his estimates of the distances he
walked from the coast. It is possible that Darwin measured the summit
elevation with a mountain barometer, an instrument he sometimes
carried with him on field trips (1839, p. 601; 1849, p. 161).
Figure 3. Darwin’s route to the summit of Santiago, showing the location of his
perfect crater (elevation 819 meters or 2,687 feet) and the summit pond (elevation
887 meters or 2,910 feet). (Image courtesy of Google Earth, ? 2006 DigitalGlobe.)
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Assuming that he reached the Santiago summit, Darwin may have
encountered water in the summit pond, as well as water draining down
from the four rivulets that run directly into this pond. He visited this
regioninOctober,inthemiddleofthegaru´aseasonwhenrainanddrizzle
are common in the highlands. In his diary, he commented about the
region near the springs: ‘‘During the greater part of each day clouds hang
over the highest land: the vapor condensed by the trees drips down like
rain. Hence we have a brightly green & damp Vegetation & muddy soil’’
(1988, p. 361). If the conditions in this region of Santiago were as wet as
Darwin described, this would be consistent with his also having found
there ‘‘muddy water’’ pools to which swarms of tortoises were attracted
from all over the island (1988, p. 362). ‘‘Near the springs,’’ Darwin (1839,
p.463)observed,‘‘itwasacuriousspectacletobeholdmanyofthesegreat
monsters;oneseteagerlytravellingonwardswithoutstretchednecks,and
another set returning, after having drunk their fill. When the tortoise
arrivesat thespring,quiteregardlessof anyspectator,itburiesits headin
the water above its eyes, and greedily swallows great mouthfuls, at the
rate of about ten in a minute.’’ Darwin also reported that tortoises were
fond of ‘‘wallowing in the mud,’’ suggesting that he observed tortoises in
pools of water, perhaps at the summit pond.
It seems likely that Darwin’s observations about the speed at which
tortoises travel were made during this same trip to the highlands of
Santiago. In his Journal of Researches, Darwin (1839, p. 464) reported
that he had clocked the speed of one large tortoise ‘‘at the rate of sixty
yardsintenminutes,thatis360inthehour,orfourmilesaday,–allowing
also a little time for it to eat on the road.’’ Calculations as to how far a
tortoise can travel in an hour, as well as in a day, are contained near the
end of Darwin’s Gala ´ pagos field notebook (1835b, p. 51b), following his
entry for 18 October, the day after he had rejoined the Beagle and sailed
toward the northwestern part of the archipelago. In his personal dairy,
however, Darwin (1988, p. 362) recorded these observations immediately
following his description of tortoises drinking at the springs.
Unlike the situation in Darwin’s day, tortoises are no longer com-
mon in the western highlands of Santiago owing to depredation by
humans and feral animals, including goats, donkeys, and pigs. (Pigs
were eradicated from this island by the Gala ´ pagos National Park
Service in 2000. Donkeys were eliminated in 2005 by marksmen firing
from helicopters, and a goat eradication campaign is currently in its
final stages – Cruz et al., 2005; Donlan et al., 2005; Nicholls and
Hooper, 2006). When the summit pond above Jaboncillos is filled with
water, this region occasionally attracts tortoises from their preferred
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haunts in Central, an area about 3 kilometers to the southeast. During
five trips to the Santiago highlands – all undertaken in dry years or
during non-garu´a conditions – I passed by the summit pond when it was
devoid of water, and only a single tortoise was ever encountered there.
During another visit, however, I detected six sets of tortoise tracks left by
one or more tortoises that had recently descended to the pond at the
center of the bowl and, after finding it dry, had exited. One of my field
assistants visited the summit pond in 1998, an El Nin ˜ o year when con-
ditions were particularly wet. At this time the pond was filled consider-
ably beyond its normal limits, and my assistant observed 20–25 tortoises
wallowing in the muddy water. Several goats and pigs were also seen
milling around nearby (Novarino Castillo, personal communication).
Based on their own investigation, Estes et al. (2000) believed that
Darwin’s springs and muddy tortoise pools were probably located
somewhere near Jaboncillos and Darwin’s perfect crater, although they
did not attempt to identify a specific location at this site, and they also
considered another location 2 kilometers to the south. Darwin, how-
ever, recorded that his perfect crater at Jaboncillos was found at an
elevation of ‘‘between 2 and 3000 ft.,’’ whereas his estimate for the
elevation for the springs and muddy pools places them somewhat
higher, at about 3,000 feet (and hence above the crater). The high point
looking down into the pond area is 2,975 feet, and the pond itself, fed by
four rivulets, is only 65 feet lower.
Although the pond area is a plausible candidate, it does not appear
to be the site of Darwin’s springs, since the term ‘‘springs’’ implies an
underground source of water, which the summit pond lacks. A much
better candidate for Darwin’s springs is an area on the northwestern
slope that connects Darwin’s perfect crater with the island’s summit.
Several dry rivulets created by drainage on this slope are located close to
the National Park trail that proceeds from Darwin’s crater to the
summit, and the small sources of running water that are sometimes
encountered at this location are mostly contained in crevices, seeping
from true underground springs (for example, at S00? 12.504¢, W90?
47.064¢, elevation 868 meters or 2,847 feet; and, more notably, at S00?
12.551¢, W90? 47.074¢, elevation 877 meters or 2,877 feet; and at S00?
12.610¢, W90? 47.099¢, elevation 883 meters or 2,896 feet). The distance
between these springs and the summit is less than 400 meters and can be
traversed in about 10 minutes (Figures 4, 5).
One of the rivulets where the springs are found descends toward the
southern edge of Darwin’s perfect crater, where it turns west as it
merges into a ravine near the base of this crater. A brief remark in
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Darwin’s pocket notebook is relevant in this connection. Under the date
12 October (but written at least one day later), he wrote: ‘‘Walked up to
the Houses – Slept there Eating Tortoise meat. By the way delicious in
Soup. – Followed down the ravine with water – soon drys: very green &
pleasant. Extraordinary numbers of Turpin [tortoises]’’ (Darwin, 1835b,
p. 36b–37b). These notes are followed by Darwin’s description of tor-
toises drinking water. Darwin’s field notes suggest that he may have
encountered large numbers of tortoises after descending along a ravine
where water was flowing. Because these ‘‘12 October’’ notes mention his
having spent the night at the Spaniard’s camp, they were written either
on 13 or 14 October and do not necessarily represent a faithful temporal
sequence, only a later recording of the most important details accu-
mulated from two days of collecting and observing. These field notes are
not therefore inconsistent with Darwin’s having climbed to the summit
of Santiago – where he may have observed swarms of tortoises near the
springs and perhaps at the summit pond – and then, during his descent,
having followed the ravine down until any drainage from the springs
ran dry.
Figure 4. This photograph, taken about 60 meters below the Santiago summit, shows
Darwin’s perfect crater (top, right) from its southeastern side. In front of the crater is
a ravine Darwin explored, which descends toward the west. Darwin’s springs are
located on this slope, close to where the author (foreground) and expedition member
Christopher Sasaki are hiking toward the summit in May 2006. (Photograph by Eric
Rorer.)
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Alternative Locations for Darwin’s Springs
There is another ravine near Jaboncillos that sometimes contains run-
ning water. This ravine is located approximately 600 meters south of the
summit pond and 1 kilometer from Darwin’s perfect crater. The ravine
descends toward the southwest and a place called Aguacate, beginning
at about S00? 12.932¢ and W90? 47.177¢; elevation 762 meters or 2,500
feet. It seems unlikely that Darwin would have walked from the summit
in this southwestern direction, as such a descent would have taken him
considerably away from the hovels, and no such descent is recorded in
his field notes. In addition, the southern flanks of Santiago’s summit
have patches of tree ferns, and Darwin (1839, p. 460) incorrectly
asserted that tree ferns are not present in the Gala ´ pagos, so we can be
reasonably confident he did not walk in this direction.
An additional candidate for Darwin’s springs is a large area to the
southeastof theisland’s summitcalled Central, whereseveral small pools
Figure 5. An enlarged section of Figure 3, showing the summit area together with a
series of springs on the northwestern slope between Darwin’s perfect crater and the
summit. The dotted line delineates those parts of the summit – the western rim of a
former and much-eroded crater – that rise above 900 meters (2,952 feet). To the right
of the summit and about 20 meters below it, is the summit pond, together with sev-
eral rivulets feeding this pond from different sides. (Image courtesy of Google Earth,
? 2006 DigitalGlobe.)
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of water are frequented by tortoises when conditions are wet. One of the
largestofthesepondsislocated1.9 miles(3.1 kilometers)tothesoutheast
of the island’s summit (at S00? 13.961¢ and W90? 44.856¢; elevation
671 meters or 2,200 feet). Estes et al. (2000) have suggested another
candidatepondatS00?13.918¢andW90?47.020¢.Thislocalityis1.4 miles
(2.3 kilometers) due south of the summit pond, and other pools of water
are also found in this area.2Nevertheless, none of these alternative loca-
tionsaccordwellwiththeavailablehistoricalevidence.Inparticular,there
is no reason to believe that Darwin ever traveled this far to the south or
east,ashemakesnoreferencetohavingundertakenfurtherexplorationof
the island beyond the summit at 3,000 feet. In addition, as Estes et al.
(2000) note, these various tortoise pools are at substantially lower eleva-
tions than Darwin reported for the springs he visited.
Denudation of Vegetation Documented by Repeat Photography
Going back more than a century, Santiago has changed radically since
Darwin’s visit owing to the introduction of feral mammals. Although
this island was never permanently settled owing to the scarcity of fresh
water, a succession of buccaneers, whalers, fishermen, and short-term
inhabitants introduced goats, donkeys, pigs, dogs, rats, and mice to the
island. This unfortunate introduction of non-native species has exerted
a significant destructive influence on this island’s vegetation as well as
on the island’s bird and reptile populations. In an effort to document
ecological degradation on Santiago and various other islands in the
Gala ´ pagos, I have used the method of repeat photography, drawing on
2Estes et al. (2000) do not report a datum for their GPS measurements. Different
datums produce measurement disparities of several hundred meters or more. Using the
WGS-84 datum, Estes et al.’s GPS site for this particular tortoise pool is located on the
steep flanks of a prominent hill and cannot be the actual locality. Relative to GPS
readings based on WGS-84 datum, the GPS measurements reported by Estes et al. are
displaced between about 50 and 1,100 meters, usually to the south, with a mean dis-
placement of about 250 meters. Corrected for this mean displacement, these GPS
readings continue to exhibit substantial deviations from known localities, with an
average disparity of more than 100 meters. These displacement statistics do not include
four measurements by Estes et al. that are off by 10, 12, 18, and 20 kilometers, owing to
transposition errors. It seems likely that the tortoise pool to which Estes et al. refer is
located at S00? 13.779¢ and W90? 46.896¢, elevation 670 meters or 2,197 feet–a
displacement of 345 meters to the north of the WGS-84 datum coordinates corre-
sponding to Estes et al.’s GPS location. This pool lies on the National Park trail from
the highlands to Aguacate. Two other pools are located 1.0 and 1.4 kilometers to the
northwest, along the same trail.
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photographs taken long ago by others and then, from the same loca-
tions, by me. This technique for detecting changes in landscapes has
been applied in a variety of research projects, including documentation
of ecological alterations in the American southwest, and the study of
glaciers (Hart and Laycock, 1996; Pickard, 2002; Rogers et al., 1984;
Webb, 1996). To implement such a project for the Gala ´ pagos Islands, I
have examined tens of thousands of images in forty collections and have
made copies of more than a thousand of the most promising candidate
images (Sulloway, 2007). The earliest existing photographic images
from the Gala ´ pagos date from the Webster-Harris Expedition
(1897–1898) and, a few years later, from the California Academy of
Sciences Expedition (1905–1906; see Beck, 1897–1906). In addition, a
small number of images (sketches and watercolors) were recorded
during the Beagle voyage (FitzRoy, 1839; Keynes, 1979).
In the course of sixteen months of field work in the Gala ´ pagos,
conducted during the last decade on thirteen islands, I have located the
original sites of more than four hundred of these images and obtained
new images for comparison. Photographs from Santiago provide evi-
dence of ecological changes going back more than seventy years. One of
the images I have located in the highlands of Santiago shows the summit
pond and surrounding vegetation in April 1970, when Japanese plant
ecologist Syuzo Itow photographed it (Figure 6a). At this time, the
pond was partially filled with water. Based on a photograph taken at
this same site in April 2007, it is apparent that feral animals have suc-
ceeded in destroying almost all of the vegetation in this part of the
island (Figure 6b, c; photographs taken at S00? 12.615¢, W90? 46.956¢;
elevation 898 meters or 2,945 feet). The specific sources of this
destruction are determinable from a closer examination of Itow’s 1970
photograph. Enlargements of portions of the image reveal the presence
of at least nine goats, a donkey, and what appear to be four or five pigs
(Figure 6d, e).
In Darwin’s day, before feral animals became widespread on
Santiago, this region would have been heavily forested, mostly with
Zanthoxylum fagara (cat’s claw), Scalesia pedunculata (tree scalesia),
epiphytes, and ferns – species that Darwin collected during his highland
visit (Hooker, 1847a, 1847b; Porter, 1980; Stewart, 1915). Darwin
(1835a, p. 723) himself noted about his perfect crater, which is about
90 meters below the site of Itow’s 1970 photograph, that it was ‘‘well
wooded’’ in the interior, something that is no longer the case today.
From the photographic comparison provided by Figure 6a, b, we have,
in effect, a partial historical glimpse of the richly forested environment
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that Darwin would have encountered at this site in 1835. In the Origin of
Species Darwin (1859) marshaled evidence of similar ecological
destruction on other originally uninhabited oceanic islands, including
Figure 6. (a) (above): The summit pond and surrounding vegetation in 1970, seen from
the summit rim, close to Darwin’s likely point of ascent. After more than a century of
depredation by feral animals, more than half of the vegetation was already denuded at
this site. (Photograph by Syuzo Itow, copyright ? Nagasaki University Library.) (b)
(below, left): The same landscape, photographed by the author in April 2007, shows
nearly 100 percent denudation of the vegetation. Several of the rivulets that drain into
the pond can be seen in this image. (c) (below, right): Enlargement of the central portion
of Figure 6b, showing a lone tortoise (Geochelone nigra darwini) resting directly in front
of a group of mules, which were attracted to the pond, like the tortoise, in the hope of
finding water. (The mules belong to the National Park Service and are used to transport
supplies to the highlands in support of the Park’s conservation efforts.)
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Figure 6, continued. (d) (above): Enlargement of the lower edge of Figure 6a, show-
ing five goats. Before the goat eradication program by the Gala ´ pagos National Park,
about 100,000 goats were present on Santiago. Goats not only destroy vegetation
that is within their reach, but they also kill mature trees by striping bark from the
trunks. A dead cat’s claw tree (Zanthoxylum fagara) is visible in this image – a sight
typical of goat-ravaged areas in the Santiago highlands. (Photograph by Syuzo Itow,
copyright ? Nagasaki University Library.) (e) (below): Enlargement of the upper,
central portion of Figure 6a, showing a donkey (upper right), a black-and-white goat
(far left), and what appears to be a group of four or five pigs in the lower, central
part of the image. (Photograph by Syuzo Itow, copyright ? Nagasaki University
Library.)
FRANK J. SULLOWAY
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St. Helena and New Zealand, to argue against the creationist theory of
Design. A few years later, Darwin sought, unsuccessfully, to obtain such
information about the Gala ´ pagos from a prospective visitor, but it
would be more than a century before biologists began to document
this process in formal studies and to undertake the kinds of analyses
that Darwin first envisioned in the Origin of Species (Darwin, 1999,
p. 404; letter to Osbert Salvin, 11 May 1863; Hamann, 1993; Itow, 2003;
Sulloway, 2006a).
Undermining the Stability of Species
Darwin’s trip to the Santiago highlands is notable in one important
respect that bears on his eventual conversion to the theory of evolution.
As is apparent from the contents of Darwin’s field notebook as well as
his later published accounts, he learned a great deal about various
Gala ´ pagos organisms from conversations with the Spaniards who were
living at the hovels. Among other things, these two men informed him
about the mating habits of the tortoise and how many eggs the females
usually lay, as well as about the habits of the Gala ´ pagos hawk (Darwin,
1835b, p. 38b–40b). Nine month’s after his Gala ´ pagos visit, as he was
making a copy of his Beagle ornithological notes for the benefit of
systematists back in England, Darwin penned what has become the
single most famous passage from this voyage owing to its first tentative
reference to the possibility of evolutionary change:
When I recollect, thefact that fromthe formof body, shape of scales
& general size, the Spaniards can at once pronounce, from which
Island any Tortoise may have been brought. When I see these is-
lands in sight of each other, & possessed of but a scanty stock of
animals, tenanted by these [mocking]birds, but slightly differing in
structure & filling the same place in Nature, I must suspect they are
only varieties.…If there is the slightest foundation for these remarks
the zoology of Archipelagos – will be well worth examining; for
such facts [would inserted] undermine the stability of Species.
(Darwin, 1963 [1836], p. 262; for the dating of this passage, see
Sulloway, 1983a)
What is particularly curious about this famous passage is Darwin’s
reference to ‘‘the Spaniards.’’ In his Journal of Researches (1839)
Darwin later credited the vice-governor of the islands, Nicholas E.
Lawson, with having alerted him to the island-to-island differences
among the tortoises. Before proceeding to Santiago, Darwin had met
TANTALIZING TORTOISES AND DARWIN-GALA´PAGOS LEGEND
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